1. Field of the Invention:
The present invention relates to an endoscope apparatus which is capable of obtaining an optical image and an ultrasonic image.
2. Related Art Statement:
In recent years, various electronic endoscopes have been proposed in which solid-state imaging devices such as charge-coupled devices (CCDs) are used as imaging means.
In addition, rapid development has been made in ultrasonic diagnosing apparatuses for diagnosing somatic tissues and organs. Recently, ultrasonic endoscopes have also been used in which probes are inserted into somatic cavities so as to allow the interior of somatic cavities to be observed endoscopically. In this ultrasonic endoscope, a vibrator is inserted into the body, and hence the tissue such as skin and the fat which attenuates ultrasonic waves is not interposed between the vibrator and an affected part to be diagnosed. Therefore, there are advantages in that the transmission of ultrasonic waves is excellent, and that it is possible to obtain images having a high degree of definition.
Furthermore, as disclosed in, for instance, Japanese Patent Laid-Open No. 133232/1983, an ultrasonic endoscope has been proposed which is arranged such that a means for obtaining an optical image such as a solid-state imaging device, and a means for obtaining an ultrasonic image are provided in a distal end portion of an inserting section, and relative positional relationships between the optical image and the ultrasonic image are clarified so as to allow the optical image and the ultrasonic image to correspond to each other.
In an endoscope apparatus which is provided with a solid-state imaging device as a means for obtaining an optical image and a vibrator as a means for obtaining an ultrasonic image, if an attempt is made to observe the optical image and the ultrasonic image simultaneously, a signal for imaging and a signal for obtaining the ultrasonic image are simultaneously transmitted and received through an elongated endoscope. This results in mutual interference of the signals, and a great amount of noise appears in the image, with the result that the image becomes difficult to observe. In particular, as for a drive pulse of the ultrasonic vibrator, a pulse value is extremely high at, for instance, 250V, so that there is a risk of pulse-like noise becoming mixed in an imaging signal line of the solid-state imaging device.
For that reason, while one image is being observed, it is possible to, for instance, completely stop the drive signal for the other image so as to prevent the mixing in of noise. In this case, however, the other image cannot be obtained at all, so that a hindrance is caused to observation. In particular, when the ultrasonic image is being observed, it is extremely important to ascertain by an optical image using the solid-state imaging device which part of the body the ultrasonic image being displayed pertains.
In addition, Japanese Patent Laid-Open No. 77731/1985 discloses a technique in which the ultrasonic oscillation is suspended during a period of reading by the solid-state imaging device. According to this related technique, the ultrasonic oscillation is suspended, for instance, during a period of 4 ms in one cycle of 33 ms. However, this period of suspension is long when compared with an ultrasonic pulse which is transmitted at a pulse width of 1 .mu.s in a cycle of 300 .mu.s, so that there is a problem in that an amount of information obtained from the ultrasonic image becomes small.
Furthermore, when a system is used in which an ultrasonic probe is made to mechanically scan to obtain an ultrasonic image, the following problem is encountered. If a motor, i.e., a driving means for causing the ultrasonic probe to mechanically scan, is driven while a drive pulse is being supplied from a solid-state imaging device driving means to a solid-state imaging device, the brush noise generated from the motor and the induction noise generated from various mechanical vibrations are induced to a signal cable for driving the solid-state imaging device. Hence, when an optical image is displayed on a monitor, the noise appears, with the result that the quality of the optical image is impaired, making it impossible to carry out proper diagnosis of the image.
On the contrary, if a drive pulse is sent to the solid-state imaging device while the motor, i.e., a driving means for causing the ultrasonic probe to mechanically scan, is being driven and a high-frequency pulse is being sent to the ultrasonic probe to effect ultrasonic scanning, the following problem is encountered. When the ultrasonic image is displayed on the monitor, noise appears on the monitor due to fluctuations in voltage caused at the time of changing over of this drive pulse, thereby causing a hindrance to proper diagnosis of the ultrasonic image.
In the above-described Japanese Patent Laid-Open No. 77731/1985, a proposal is made not to send the high-frequency pulse to the ultrasonic probe while the drive pulse is being supplied to the solid-state imaging device and reading of the signal is being carried out. However, since the motor for rotatively driving the ultrasonic probe is constantly operating, noise generated therefrom is not removed. A known apparatus is arranged such that an optical image observing apparatus and an ultrasonic image observing apparatus are operated by being changed over by means of two changeover switches so as to obviate the mutual interference caused by such noise. However, since the two changeover switches are not interlinked with each other, the operation is complicated, and has been particularly troublesome when the optical image and the ultrasonic image are changed over frequently.